Assessing and affording the control of flood risk

Flood is a most serious hazard to life and property. Dams, dikes and levees are often designed to a fuzzy quantity (PMF). Probabilistic design is preferable but requires that hydrological data be translated into a local monoscopic flood probability distribution. This process introduces information that goes beyond the facts. The method of relative entropy with quantile constraints minimizes this information and has a practical approximation, which is used here.Socio-economic optimization provides a design criterion that reflects the societal capacity to commit resources (SCCR) to sustainable risk reduction. Details of financing have an important influence on the design of flood control projects by socio-economic optimization; since future life risk must be discounted like finances, the interest rate and amortization period influence design decisively. The example of a city protected by a levee casts a light on the relative importance of the factors influencing the design.